userList = list();

userEntry1 = map();
userMap1 = map();
userMap1.put("id", "5971686000090743029");  // The actual User ID
userEntry1.put("Sales_Manager", userMap1);  // MUST match the field API name again
userList.add(userEntry1);

updateMap = map();
updateMap.put("Sales_Manager", userList);  // Field name (multi-user field)

dataList = list();
dataList.add(updateMap);

bodyMap = map();
bodyMap.put("data", dataList);
response = invokeurl
[
    url: "https://www.zohoapis.com/crm/v5/Leads/5971686000084102043"
    type: PUT
    parameters: bodyMap.toString()
    connection: "newzohocrm"
];
info response;